This invention relates to optical instrumentation and to the optical measurement of surface qualities and characteristics. In particular there exists today instruments to study surfaces by reflective techniques. These provide measurements of various characteristics and/or qualities of surfaces and of thin film layers that are at least partially light transmissive when deposited on a substrate. A surface for measurement may comprise the surface of a hard disk or a computer memory which initially may comprise a metallic or glass support layer and deposited coating layers of magnetic media with a final layer of carbon and a lubricant layer deposited onto the surface of the disk on the carbon layer.
One form of instrument for optical diagnostics is known as a reflection ellipsometer. Another is known as a polarization-modulated ellipsometer. However, these units are relatively slow and not useful in situations demanding real time measurements of a sample including large amounts of data.
An instrument that can be used for real time detection and analysis is called a Surface Reflectance Analyzer. It is capable of optically scanning the entire surface of a sample providing measurement data and visual images of a wide range of surface properties in a matter of seconds. It provides real time access to large amounts of data that define surfaces and layer characteristics. Such an instrument is described, for example, in U.S. Pat. No. 6,307,627, and such instruments are sold by HDI Instrumentation of Santa Clara, Calif. It is this type of instrument to which the improvements of the invention are directed.
Surface Reflectance Analyzers use an intensity stabilized light source that is directed to and reflected from a surface being studied. It provides in a single scan sufficient data as to enable a comprehensive and a sophisticated analysis. The system may measure three or more sample related parameters simultaneously. In practice, the specularly reflected light beam from the surface being studied is converted into its s and p polar components for measurement purposes. At least a third component is also typically measured simultaneously, which may for example be the scattered light from the surface. Modern equipment uses an integrating sphere to pick up, gather, and detect the scattered light. Such a structure for example is shown in FIG. 2 of U.S. Pat. No. 6,134,011. This same patent also describes the use of a laser which today typically appears in commercial units. It produces a stable output at 670 nm. Since all measurements are made simultaneously, real time measurements and determinations of desired parameters can and become available immediately. The instrument may be used, for example, in studies of hard memory disks for computer systems, semiconductor layers, photonics and surfaces used in medical applications. In operation, one can create, in a single pass, a map of the entire surface being examined as to show residues, scratches, waviness, particles, film thickness uniformity, etc. For example in working with a computer disk following a polishing operation in the manufacture of the disk, one can determine whether the surface finish meets the requirements for the product. The instrument may also be used for the measurement of the thickness and other characteristics of a deposited coating and can visually display surface smoothness, waviness and uniformity variations, among other things. Thus one has the capability, for example, of simultaneously analyzing p polar, s polar, Phase Contrast, Scattered, Circumferential and Radial parameters in seconds in studying a surface or layer.